128 



distinct or easily separable forms and not members of a fluctuat- 

 ing series. 



0. Lamarckiana of de Vries has 26-46 per cent, fertile seed and 

 throws only a few mutants. Davis's neo-Lamarckiana, on the 

 other hand, was highly fertile (87 per cent.), and gave a large 

 numljer of "mutants," almost twice as many as plants resembling 

 the parent. Davis believes that the reduction of the fertility 

 of neo-Lamarckiana to that of Lamarckiana might readily result 

 in the production of fewer mutants, thus paralleling the condi- 

 tion found among the true Lamarckiana offspring. 



There is, however, no question but that Davis has produced 



a form which morphologically closely resembles de Vries's 



Lamarckiana. 



H. M. Boas 



MechanUm of Tumor Growth In Crown Gall* 



In attempting to arrive at an explanation of the behavior 

 of the host cells in the formation of crowngall. Smith comes to 

 the conclusion that while the ultimate cause of cell proliferation 

 is the organism Bacterium tiimefaciens, the proximate cause must 

 be the release within the cells of the host, by the bacterium, of 

 one or more products of its metabolism. 



On an artificial medium consisting of agar, water, calcium 

 carbonate, grape sugar and peptone, Bact. tiimefaciens produces 

 chiefly ammonia and alcohol. With this fact as a clue Smith 

 subjected plants to the action of various ammonia compounds, 

 the chief methods being to inject the hollow stem of the castor 

 bean plant, and young tomato fruits, with variously diluted 

 solutions of the compounds and to expose the leaves of cauli- 

 flower plants to the fumes of the ammonia compounds, or to 

 paint the solutions directly on the leaf. 



In practically all cases striking proliferations occurred, the 

 internal structure and outward appearance of which was identical 

 with early stages of crown gall as produced by Bact. tumefaceins. 

 Subsequent experiments demonstrated that this action is not 

 restricted to ammonia compounds, but that it is characteristic 



* Smith, Erwin F. Mechanism of Tumor Growth in Crowngall. Journ. Agric. 

 Research, 8, 165-186 + 62 pis. igi?-. 



